core: Only perform PCI config space writes on PCI_ACCESS_PERFORM

core: Only perform PCI config space writes on PCI_ACCESS_PERFORM

If we emulate a config space write, we may be able to skip the physical
access completely. To model this, rename PCI_ACCESS_EMULATE to
PCI_ACCESS_DONE which signals to the caller of the moderation functions
that no physical access should be performed.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>